Japanese Knotweed When to Treat it?

One of the most crucial aspects of any herbicide treatment is timing it correctly within the growing season. This actually applies to the treatment of a great many problem species both plant and insect when applying chemicals as a means of control but it’s particularly crucial when it comes to Japanese Knotweed.

At present the marauding stand of Knotweed which has been gradually taking over your land for the last four or five months probably has it’s pretty face on with large ‘sprays’ of flowers such as those in the picture above brightening up the otherwise imposing and impenetrable bulk of vegetation. This is a signal that if you’re going to use one of the most common and effective forms of treatment it’s probably about time to contact a suitably qualified person who will break out the glyphosate based herbicide and schedule in a treatment. Crucially this decision must be made based on the appearance of the plant rather than an arbitrary date in the calendar, the British weather is a curious thing and unseasonable weather will affect the growth of most plants.

Because of the way Japanese Knotweed grows a mistimed treatment risks either killing the surface growth without significantly impacting the buried rhizome if you treat too early. Or if you treat too late you risk not effectively transporting the chemical into the rhizome because the plant has started dying back. Systemic herbicides such as glyphosate need the plant to be alive so that the chemical can move along with the normal fluid movements inside the plant and reach the rhizome (the root of the problem if you’ll pardon the pun), to be most effective. It should be pointed out that in both these scenarios as long as the plant is of a reasonable size and the leaves and stem are still green the herbicide treatment will have some effect you just won’t get the same bang for your buck as a treatment within the optimum window.

So the ideal time to treat is probably about now if the treatment plan is to use a glyphosate based herbicide. The optimum timing for other herbicides will be different and it is a crucial legal requirement that anyone applying pesticides in a commercial context is suitably qualified and that they do so in accordance with the licence of the product. There are likely to be other considerations such as the weather, pollinating insects and human activities in the vicinity to be managed as well. So, as with so much in life timing really is everything and a suitably qualified professional is the best person to take these decisions. If you want to know more just drop us an email or give us a call on 0800 02 09 307.

Guide to Japanese Knotweed

This free guide will help you learn about Japanese knotweed and how to treat it in the simplest terms. Download it now for free!